Removing prerender dead code.

chrome/browser/prerender/prerender_tab_helper.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/prerender/prerender_tab_helper.h"
 
 #include "base/metrics/histogram.h"
 #include "base/string_number_conversions.h"
 #include "base/time.h"
 #include "chrome/browser/prerender/prerender_histograms.h"
@@ skipping 113 matching lines @@
   // and the WebContents that it was swapped into.
   scoped_ptr<SkBitmap> bitmap_;
   WebContents* bitmap_web_contents_;
 
   base::WeakPtrFactory<PixelStats> weak_factory_;
 
   PrerenderTabHelper* tab_helper_;
 };
 
 PrerenderTabHelper::PrerenderTabHelper(TabContents* tab)
-    : content::WebContentsObserver(tab->web_contents()),
-      tab_(tab) {
+    : content::WebContentsObserver(tab->web_contents()) {
 }
 
 PrerenderTabHelper::~PrerenderTabHelper() {
 }
 
 void PrerenderTabHelper::ProvisionalChangeToMainFrameUrl(
     const GURL& url,
     const GURL& opener_url,
     content::RenderViewHost* render_view_host) {
   url_ = url;
@@ skipping 99 matching lines @@
     // If we have not finished loading yet, record the actual load start, and
     // rebase the start time to now.
     actual_load_start_ = pplt_load_start_;
     pplt_load_start_ = base::TimeTicks::Now();
     if (pixel_stats_.get())
       pixel_stats_->GetBitmap(PixelStats::BITMAP_SWAP_IN, web_contents());
   }
 }
 
 }  // namespace prerender